The above example raises other questions such as how one would validate an html array. In the input form each input tag that refers to an html array would be named for example testarray[]. However, after the form is submitted, the syntax for validating the values is different from the expected $_POST['testarray[]']. Instead one has to drop the braces and validate as follows, assuming that testarray[] is supposed to be an html array of numerical values:

So, there is a naming inconsistency going on, as after the form is submitted, one has to forget about the original name of the submitted array by dropping its braces. Maybe when the PECL/Filter extension is reviewed again, the great ones might consider making the syntax a little more forgiving.